The present invention relates to chromophores which can be used in the preparation of polymeric thin films for waveguide media, and to optical waveguides and devices comprising the chromophores.
Thin films of organic or polymeric materials with large second order nonlinearities in combination with silicon-based electronic circuitry can be used in systems for laser modulation and deflection, information control in optical circuitry, as well as in numerous other waveguide applications. In addition, novel processes through third order nonlinearity such as degenerate four-wave mixing, whereby real-time processing of optical fields occurs, have utility in such diverse fields as optical communications and integrated circuit fabrication. The utility of organic materials with large second order and third order nonlinearities for very high frequency application contrasts with the bandwidth limitations of conventional inorganic electrooptic materials currently in use.
Numerous optically responsive monomers and polymers have been developed for use in organic materials which, in turn, can be used in the waveguide applications described above. For example, U.S. Pat. No. 5,044,725, which is incorporated herein by reference in its entirety, describes numerous polymer compositions which provide suitable nonlinear optical response. U.S. Pat. No. 5,044,725 describes, for example, a preferred polymer composition comprising an organic chromophore containing an electron donating group and an electron withdrawing group at opposing termini of a bridge.
Synthesis of high performance organic, high xcexcxcex2 electro-optic chromophores must be accomplished in order to make polymer-based electro-optic waveguides and devices. The synthesis of electro-optic chromophore bridge compounds and donor-bridge compounds for organic nonlinear optical applications are generally known in the art. Although some chromophores have been reported in the literature, many of them have shown several and sometimes severe problems ranging from thermal instability, insolubility in the polymer, photodegradability, exhibition of a broad absorption band into the wavelength region of interest, and large birefringence upon poling.
Most recently, U.S. Pat. No. 6,067,186 (the ""186 patent), disclosed a class of organic chromophors which can result in hardened electro-optic polymers suitable for electro-optic modulators and other devices such as optical switch.
There continues to be a need for suitable electro-optic chromophores with improved properties.
The present invention is directed, in part, to compounds which can serve as chromophores in, for example, thin films for optical waveguides and optical devices. These are compounds represented by Formula I: 
wherein:
D is an electron donating group;
B comprises at least one bivalent ring; and
R2 and R3 each, independently, are selected from the group consisting of substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C2-C10 alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted alkylaryl, substituted or unsubstituted carbocycle, substituted or unsubstituted heterocycle, substituted or unsubstituted cyclohexyl, and (CH2)nxe2x80x94Oxe2x80x94(CH2)n where n is 1-10. Alternatively, R2 and R3 can be selected from substituted or unsubstituted C2-C10 alkyl, provided that when R2 and R3 are both selected from substituted or unsubstituted C1-C1 alkyl the following condition is also met: R2xe2x89xa0R3. More preferably, chromophores of the invention have Formula Ixe2x80x2: 
xe2x80x83where:
R2 and R3 are further characterized in that they define a ring in which * denotes a spiro junction, or where * denotes a chiral center; D and B have the definitions given above; and R2 and R3 each, independently, are either, substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C2-C10 alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted alkylaryl, substituted or unsubstituted carbocyclic, substituted or unsubstituted heterocyclic, substituted or unsubstituted cyclohexyl, or (CH2)nxe2x80x94Oxe2x80x94(CH2)n, where n is 1-10.
In still another aspect of the invention, the chromophores comprise novel cyclic bridges comprising at least one bivalent aromatic ring. Preferred compounds of the invention have Formula II: 
wherein D is an electron donating group; A is an electron withdrawing group; K is O or S;
R1 is xe2x80x94Qxe2x80x94CnH2n+1, xe2x80x94Qxe2x80x94(CH2)aCCnF2n+1, xe2x80x94Qxe2x80x94CH2OCH2CnF2n+1, xe2x80x94Qxe2x80x94CH2SCH2CCnF2n+1, xe2x80x94Qxe2x80x94CH2OCH2CF3, or xe2x80x94Qxe2x80x94CH2SCH2CF3, where n is 1-10, a is 0-10, and Q is absent, O or S; and q is 1, 2, or 3.
Other preferred compounds of the invention have Formula III: 
wherein D is an electron donating group; A is an electron withdrawing group; J is CH2, O or S; R1 is xe2x80x94Qxe2x80x94CnH2n+1, xe2x80x94Qxe2x80x94(CH2)aCnF2n+1, xe2x80x94Qxe2x80x94CH2OCH2CnF2n+1, xe2x80x94Qxe2x80x94CH2SCH2CCnF2n+1, xe2x80x94Qxe2x80x94CH2OCH2CF3, or xe2x80x94Qxe2x80x94CH2SCH2CF3, where n is 1-10, a is 0-10, and Q is absent, O or S.
In other embodiments of the invention, the chromophores comprise novel cyclic bridges comprising at least one bivalent or conjugated ring structure, such as an aromatic ring, and novel electron withdrawing groups. Such compounds are generally represented by the structure of Formula IV: 
wherein D is an electron donating group; K is O or S; R1 is xe2x80x94Qxe2x80x94CnH2n+1, xe2x80x94Qxe2x80x94(CH2)aCnF2n+1, xe2x80x94Qxe2x80x94CH2OCH2CnF2n+1, xe2x80x94Qxe2x80x94CH2SCH2CCnF2n+1, xe2x80x94Qxe2x80x94CH2OCH2CF3, or xe2x80x94Qxe2x80x94CH2SCH2CF3, where n is 1-10, a is 0-10, and Q is absent, O or S; q is 1, 2, or 3; and R2 and R3 each, independently, are either substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C2-C10 alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted alkylaryl, substituted or unsubstituted carbocycle, substituted or unsubstituted heterocycle, substituted or unsubstituted cyclohexyl, or (CH2)nxe2x80x94Oxe2x80x94(CH2)n where n is 1-10. Alternatively, R2 and R3 together form a ring structure or a substituted ring structure. Preferred compounds of this embodiment are represented by the structure of Formula IVxe2x80x2: 
xe2x80x83where:
R2 and R3 are further characterized in that they define a ring in which * denotes a spiro junction, or where * denotes a chiral center.
Other useful compounds of the invention have Formula V: 
wherein D is an electron donating group; J is CH2, O or S; R1 is xe2x80x94Qxe2x80x94CnH2n+1, xe2x80x94Qxe2x80x94(CH2)aCnF2n+1, xe2x80x94Qxe2x80x94CH2OCH2CnF2n+1, xe2x80x94Qxe2x80x94CH2SCH2CCnF2n+1, xe2x80x94Qxe2x80x94CH2OCH2CF3, or xe2x80x94Qxe2x80x94CH2SCH2CF3, where n is 1-10, a is 0-10, and Q is absent, O or S; and R2 and R3 each, independently, are either H, substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C2-C10 alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted alkylaryl, substituted or unsubstituted carbocycle, substituted or unsubstituted heterocycle, substituted or unsubstituted cyclohexyl, or (CH2)nxe2x80x94Oxe2x80x94(CH2)n where n is 1-10. Alternatively, R2 and R3 together form a ring structure or a substituted ring structure. Preferred chromophores of this embodiment include compounds of Formula (Vxe2x80x2): 
where:
R2 and R3 are further characterized in that they define a ring in which * denotes a spiro junction, or where * denotes a chiral center.
The present invention is also directed to optical waveguides comprising a thin film medium having Formula VI: 
wherein P and Pxe2x80x2 are polymer main chain units, which can be the same mer unit or different mer unit, and C is a comonomer unit where n is an integer greater than zero and nxe2x80x2 is 0 or an integer greater than zero; S is a pendant spacer group having a linear chain length of between about 2-12 atoms. M is a compound having either Formula I, Formula II, Formula III, Formula IV, or Formula V, as described above.
The phrase xe2x80x9celectron donating groupxe2x80x9d is used synonymously with xe2x80x9celectron donatorxe2x80x9d and refers to substituents which contribute electron density to the xcfx80-electron system when the conjugated electron structure is polarized by the input of electromagnetic energy.
The phrase xe2x80x9celectron withdrawing groupxe2x80x9d is used synonymously with xe2x80x9celectron accepting groupxe2x80x9d and xe2x80x9celectron acceptorxe2x80x9d and refers to electronegative organic compounds or substituents which attract electron density from the xcfx80-electron system when the conjugated electron structure is polarized by the input of electromagnetic energy.
The term xe2x80x9cchromophorexe2x80x9d as used herein refers to an optical compound comprising an electron donating group and an electron withdrawing group at opposing termini of a conjugated xcfx80-electron system.
The phrase xe2x80x9ccyclic bridgexe2x80x9d is used to refer to bivalent cyclic structures which serve to couple the electron donating and withdrawing groups.
The present invention is also directed to optical devices comprising the optical waveguides described above.
The present invention is directed, in part, to novel electro-optic chromophores which have utility in organic nonlinear optical applications such as polymeric thin films for optical waveguides and optical devices. Such polymeric thin films are described in, for example, U.S. Pat. Nos. 5,044,725, 4,795,664, 5,247,042, 5,196,509, 4,810,338, 4,936,645, 4,767,169, 5,326,661, 5,187,234, 5,170,461, 5,133,037, 5,106,211, and 5,006,285, each of which is incorporated herein by reference in its entirety.
The inventive chromophores have several advantageous features which are not found in other known or commercially available chromophores. For example, we have found that the introduction of a chiral center, preferably in the acceptor portion of the molecule, and more preferably as a racemic mixture, greatly increases the chromophore""s solubility. We have found that solubility is enhanced the greater the structural or functional differences between R2 and R3. For example, we have observed significantly enhanced solubility when one of R2 or R3 is a chain and the other is a ring structure; or when one is a short chain (up to three carbons), and the other is a long chain (say, C4-C18). This increased solubility in turn can lead to an enhanced nonlinearity of the final material in many cases. It is known that the introduction of long chain alkane groups increase the solubility of chromophores, and that as the number and size of the alkane moieties increase, both the solubility and bulk material nonlinearity are greatly improved. The chromophores of the present invention have an enhanced solubility over the dimethyl types of the prior art.
While there may be other factors contributing to this improved property, we have found that one major difference between the inventive acceptors and those of the prior art is the presence of chiral centers in the inventive acceptors. It is known that the physical characteristics like melting point and solubility are different for the pure enantiomer than for the racemic mixture. Several examples of this difference exist. For example, pure chiral (D) lycine has a melting point of 218 C and is very soluble at room temperature. The racimate has a melting point of 170 C and is considered infinitely soluble in room temperature water. Also, pure enantiomers of Mandelic acid have a melting point of 133 C while the racimate has a melting pint of 120 C. (R)-(+)-Mandelonirile has a melting point of 29 C while the racimate is an oil at room temperature.
In the specific chemistry of the present invention, the chiral centers do not form a single chiral compound but rather a mixture of racemic enantiomers, which when introduced into chromophores increase the solubility of the chromophores due to a depression of the melting point. In fact, we have found that the inventive compounds tend to form glassy solids rather than crystalline materials. Without intending to be bound by theory, we believe that the present chemistry results in improvements in the nonlinearity of the bulk polymer because of the incorporation of a racemic chiral center in the chromophores.
The electro-optic chromophores of the invention exhibit thermal stability to temperatures from 260xc2x0 C. to 310xc2x0 C. These chromophores also show great solubility in most common organic solvents and, thus, are useful when used as a guest additive in most polymer films for waveguides. In addition, under intense UV-irradiation (365 nm, dosage 3 J/cm2 up to 13 minutes), the chromophores of the invention show no changes of the UV-VIS-NIR spectrum, which indicates that the chromophores are photostable. The chromophores also demonstrate an adjustable absorption band away from normal communications wavelenghts, which can be very important for reducing optical loss at communication wavelengths. The chromophores of the invention have significant three-dimensional design which can prevent chromophore-chromophore anti-parallel stacking. Because of the flexible side chain substitutions, the chromophores of the invention show significantly reduced birefringence losses. In some of the chromophores of the invention, there is unique regiospecific substitution on the bridging thiophene ring, which allows the electron acceptor to more easily access the conjugated xcfx80-system of the bridge and allows the molecule backbone to be flatter. In addition, some of the preferred chromophores of the invention have hydroxyl groups on the electron donor termini in order to easily process the chromophore into hydroxyl compatible organic and inorganic polymer reactions to make soluble chromophores, polymers and copolymers, as well as can be used to make highly soluble xe2x80x9cguestxe2x80x9d chromophores for guest-host applications.
The present invention is directed, in part, to compounds which can be employed as chromophores in polymeric thin films for optical waveguides. In preferred embodiments of the invention, such compounds comprise novel electron withdrawing groups having Formula I: 
where: D is an electron donating group. Preferred electron donating groups are described in, for example, U.S. Pat. Nos. 5,044,725, 4,795,664, 5,247,042, 5,196,509, 4,810,338, 4,936,645, 4,767,169, 5,326,661, 5,187,234, 5,170,461, 5,133,037, 5,106,211, and 5,006,285, each of which is incorporated herein by reference in its entirety. Preferably, D is selected from the group consisting of, but not limited to, phenyl ring(s) substituted in the para position by, for example, amino, alkylamino, dialkylamino, dialkylanilino, 1-piperidino, 1-piperazino, 1-pyrrolidino, acylamino, hydroxyl, thiolo, alkylthio, arylthio, alkoxy, aryloxy, acyloxy, alkyl, vinyl, 1,2,3,4-tetrahydroquinolinyl, and the like. The most preferred electron donating groups are substituted and unsubstituted-phenyl-N(CH2CH2OH)2.
B is a cyclic bridge which couples the electron withdrawing group and the electron donating group. Preferably, B is at least one bivalent ring. Preferred cyclic bridges comprise one or a plurality of bivalent rings. Preferred bivalent rings which can be employed as cyclic bridges in the present application are described in, for example, U.S. Pat. Nos. 5,044,725, 4,795,664, 5,247,042, 5,196,509, 4,810,338, 4,936,645, 4,767,169, 5,326,661, 5,187,234, 5,170,461, 5,133,037, 5,106,211, and 5,006,285, each of which is incorporated herein by reference in its entirety. Ring B can be aromatic or non-aromatic. Preferably, B is selected from the group consisting of, but not limited to, 
where R4 is H, OH, C1-C10 alkyl, alkenyl, or alkynyl, halogen, and the like. R4 can also be xe2x80x94Qxe2x80x94CnH2n+1, xe2x80x94Qxe2x80x94(CH2)aCnF2n+1, xe2x80x94Qxe2x80x94CH2OCH2CnF2n+1, xe2x80x94Qxe2x80x94CH2SCH2CCnF2n+1, xe2x80x94Qxe2x80x94CH2OCH2CF3, or xe2x80x94Qxe2x80x94CH2SCH2CF3, where n is 1-10, a is 0-10, and Q is absent, O or S; and q is 1, 2, or 3.
R2 and R3 each, independently, are selected from the group consisting of, but not limited to, substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C2-C10 alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted alkylaryl, substituted or unsubstituted carbocycle, substituted or unsubstituted heterocycle, substituted or unsubstituted cyclohexyl, (CH2)nxe2x80x94Oxe2x80x94(CH2)n where n is 1-10, and the like. xe2x80x9cC1-C10xe2x80x9d refers to C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, and all combinations of ranges thereof. Preferably, when R2 and R3 are both selected from substituted or unsubstituted C1-C10 alkyl the following condition is also met: R2xe2x89xa0R3. More preferably, R2 and R3 define a ring in which * denotes a spiro junction, or where * denotes a chiral center.
The substituted alkyl, alkenyl, alkynyl, carbocyclic, and heterocyclic groups can comprise one or a plurality of substituents including, for example, fluorine, chlorine, D, and the like. In addition, the heterocyclic groups can comprise O, N, S, and the like.
The aryl groups preferably include, but are not limited to, benzyl, phenyl, fluorenyl, and naphthyl. The aryl groups, carbocycles, heterocycles, and cyclohexyl can also be substituted by one or a plurality of substituents including, for example, D, halides, including fluorine, chlorine and bromine. The alkylaryl groups preferably comprise C1-C10 alkyl and the substituted alkylaryl groups comprise the substitutions for the alkyl and aryl groups described above.
In more preferred embodiments of the invention, R2 and R3 each, independently, are selected from the group consisting of benzyl, carbocycle, heterocycle, cyclohexyl, phenyl, cycloalkyl, cycloalkenyl, and substituted phenyl. Additional moieties for R2 and/or R3, independently, include, but are not limited to the following: 
and the like.
In even more preferred embodiments of the invention, one of R2 and R3 is CH3 and the other of R2 and R3 is a substituted phenyl. Preferably, the substituted phenyl is selected from the group consisting of, but not limited to: 
and the like.
Alternatively, R2 and R3 together form a ring structure or a substituted ring structure from 3 to 7 atoms total with 5 or 6 atoms being preferred. Preferably, the ring structure is substituted or unsubstituted carbocycle, substituted or unsubstituted heterocycle, or substituted or unsubstituted cyclohexyl or cyclopentyl. The substituted ring structure can comprise substituents including, but not limited to, halides, including fluorine, chlorine and bromine. A preferred compound having a ring structure formed by R2 and R3 comprises 
The electron withdrawing groups of the present invention are preferably prepared according to Scheme I: 
Compounds having Formula I are preferably prepared by the following steps depicted in Scheme I: a) providing an alkylvinylether, b) contacting the alkylvinylether with a strong base to form a first intermediate compound, c) contacting the first intermediate compound with a ketone to form a second intermediate compound, and d) reacting the second intermediate compound with dicyanomethane in the presence of a second base to form an electron withdrawing group portion of a compound having Formula I. Each of the above mentioned steps is described in greater detail below.
In preferred embodiments of the invention, an alkylvinylether in a solvent is the starting material. The solvent is, preferably, tetrahydrofuran (THF), 1,4-dioxane, or the like. Although the alkylvinylether depicted in Scheme I is ethylvinylether, other alkylvinylethers can be used. The alkylvinylether preferably comprises the formula CH3xe2x80x94(CH2)xxe2x80x94Oxe2x80x94CHxe2x95x90CHR6, where x is 1-3 and R6 is C1-C4 alkyl. Most preferably, the alkylvinylether is methylvinylether or ethylvinylether.
The alkylvinylether is contacted with a strong base to form a first intermediate compound. Preferably, the strong base has a pKa greater than the ethylinic Cxe2x80x94H bond xcex1 to the oxygen function of the alkylvinylether. For example, see Advanced Organic Chemistry, Third Ed., Jerry March, 1985, Table 1, pp. 220-222. In preferred embodiments of the invention, the strong base is an alkyl lithium, or an alkali metal salt of an alkyl anion, including, but not limited to, t-BuLi or sec-BuLi. The alkylvinylether is preferably contacted with the strong base between about xe2x88x9270xc2x0 C. and xe2x88x9285xc2x0 C., most preferably at about xe2x88x9278xc2x0 C.
The first intermediate compound is contacted with a ketone and an acid/alcohol/water solution to form a second intermediate compound. Numerous acid/alcohol/water solutions known to those skilled in the art can be used in the present invention. The acid/alcohol/water solution is preferably HCl/MeOH/H2O, HBr/EtOH/H2O, or H2SO4/EtOH/H2O. Preferably, the contacting is at room temperature. Preferably, the pH is adjusted between 1 and 4.
Preferably, the ketone comprises R3xe2x80x94C(xe2x95x90O)R2, wherein R2 and R3 each, independently, are selected from the group consisting of, substituted and unsubstituted C10 alkyl, substituted and unsubstituted C1-C10 alkenyl, substituted and unsubstituted C10 alkynyl, substituted and unsubstituted aryl, substituted and unsubstituted alkylaryl, substituted and unsubstituted carbocycle, substituted and unsubstituted heterocycle, substituted and unsubstituted cyclohexyl, and (CH2)nxe2x80x94Oxe2x80x94(CH2)n where n is 1-10.
xe2x80x9cC1-C10xe2x80x9d refers to C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, and all combinations of ranges thereof.
Preferably, the Cxe2x95x90C and Cxe2x89xa1C bonds of the alkenyl and alkynyl groups are not immediately adjacent or conjugated to the carbonyl group of the ketone compound.
The substituted alkyl, alkenyl, alkynyl, carbocyclic, and heterocyclic groups can comprise one or a plurality of substituents including, for example, fluorine, chlorine, D, and the like. In addition, the heterocyclic groups can comprise O, N, S, and the like.
The aryl groups preferably include, but are not limited to, benzyl, phenyl, fluorenyl, and naphthyl. The aryl groups, carbocycles, heterocycles, and cyclohexyl can also be substituted by one or a plurality of substituents including, for example, D, halides, including fluorine, chlorine and bromine. The alkylaryl groups preferably comprise C1-C10 alkyl and the substituted alkylaryl groups comprise the substitutions for the alkyl and aryl groups described above.
In more preferred embodiments of the invention, R2 and R3 each, independently, are selected from the group consisting of benzyl, carbocycle, heterocycle, cyclohexyl, phenyl, cycloalkyl, cycloalkenyl, and substituted phenyl. Additional moieties for R2 and/or R3, independently, include, but are not limited to the following: 
and the like.
In even more preferred embodiments of the invention, one of R2 and R3 is CH3 and the other of R2 and R3 is a substituted phenyl. Preferably, the substituted phenyl is selected from the group consisting of, but not limited to: 
and the like.
Alternatively, R2 and R3 together form a ring structure or a substituted ring structure from 3 to 7 atoms total with 5 or 6 atoms being preferred. Preferably, the ring structure is substituted or unsubstituted carbocycle, substituted or unsubstituted heterocycle, or substituted or unsubstituted cyclohexyl or cyclopentyl. The substituted ring structure can comprise substituents including, but not limited to, halides, including fluorine, chlorine and bromine. A preferred compound having a ring structure formed by R2 and R3 comprises 
The second intermediate compound is reacted with dicyanomethane in the presence of a second base to form the electron withdrawing group portion of a compound having Formula I. The second base is preferably a metal alkoxide including, but not limited to, NaOC2H5. After contacting the second intermediate compound with dicyanomethane in the presence of a second base, dilute acid such as, for example, HCl, is added for neutralization of the resultant electron withdrawing group.
The electron withdrawing group comprises R6 which is preferably selected from the group consisting of unbranched substituted or unsubstituted C1-C4 alkyl, unbranched substituted or unsubstituted C2-C4 alkenyl, unbranched substituted or unsubstituted C2-C4 alkynyl. The substituted alkyl, alkenyl, and alkynyl groups can comprise one or a plurality of substituents including, for example, fluorine. In preferred embodiments of the invention, R6 is selected from the group consisting of unbranched C1-C4 alkyl, C1-C4 alkenyl, and C1-C4 alkynyl. In more preferred embodiments of the invention, R6 is CH3.
The present invention is also directed, in part, to compounds which can be employed as chromophores in polymeric thin films for optical waveguides wherein the compounds comprise novel bridge groups which couple the electron withdrawing and donating groups of the chromophore. Preferred compounds of the invention have Formula II: 
D is an electron donating group. Preferred electron donating groups are described above.
A is an electron withdrawing group. Preferred electron withdrawing groups are described in, for example, U.S. Pat. Nos. 5,044,725, 4,795,664, 5,247,042, 5,196,509, 4,810,338, 4,936,645, 4,767,169, 5,326,661, 5,187,234, 5,170,461, 5,133,037, 5,106,211, and 5,006,285, each of which is incorporated herein by reference in its entirety. Preferably, A is selected from the group of molecular units containing, but not limited to, nitro, cyano, haloalkyl, acyl, carboxy, aryloxy, carboxamido, alkoxysulfonyl, aryloxysulfonyl, xe2x80x94CHxe2x95x90C(CN)2, xe2x80x94C(CN)xe2x95x90C(CN)2, SO2CF3, alkanoyloxy, 
where X is H, D, F, CN, NO2, or CF3.
R1 is xe2x80x94Qxe2x80x94CnH2n+1, xe2x80x94Qxe2x80x94(CH2)aCnF2n+1, xe2x80x94Qxe2x80x94CH2OCH2CnF2n+1, xe2x80x94Qxe2x80x94CH2SCH2CCnF2n+1, xe2x80x94Qxe2x80x94CH2OCH2CF3, or xe2x80x94Qxe2x80x94CH2SCH2CF3, where n is 1-10, a is 0-10, and Q preferably is either absent or, when present, O or S; q is 1, 2, or 3. More preferably, R1 is C4-C10 or fluorine substituted C4-C10.
A compound having Formula II can be prepared using a thiophene cyclic bridge which preferably comprises Formula VII: 
Preferably, K is O or S.
Preferably, R1 is xe2x80x94Qxe2x80x94CnH2n+1, xe2x80x94Qxe2x80x94(CH2)aCnF2n+1, xe2x80x94Qxe2x80x94CH2OCH2CnF2n+1, xe2x80x94Qxe2x80x94CH2SCH2CCnF2n+1, xe2x80x94Qxe2x80x94CH2OCH2CF3, or xe2x80x94Qxe2x80x94CH2SCH2CF3, where n is 1-10, a is 0-10, and Q preferably is either absent or, when present, O or S. Other halogens or deuterium can be used in place of F. In more preferred embodiments of the invention, R1 is C4-C10 or fluorine substituted C4-C10.
X preferably has the formula xe2x80x94(CHxe2x95x90CH)bxe2x80x94C(xe2x95x90O)H, where b is 0-3. The terminal aldehyde group serves as the preferred site of reaction with electron withdrawing groups.
In more preferred embodiments of the invention, b is 0 so that X is xe2x80x94C(xe2x95x90O)H.
Z is a chemical group that is capable of being linked to a donor and includes, but is not limited to, Br, I, xe2x80x94CH2xe2x80x94Br, xe2x80x94CH2xe2x80x94OH, xe2x80x94CH3, xe2x80x94C(xe2x95x90O)H, and the like. Those skilled in the art can use additional groups known to those skilled in the art to couple a bridge compound to a donor. Another Z group that can be used to link a bridge compound to a donor is 
where Yxe2x88x92 is a counter ion including, but not limited to, Brxe2x88x92 or Clxe2x88x92.
In other embodiments of the invention, preferred compounds of the invention have Formula III: 
D is an electron donating group and A is an electron withdrawing group as described above. J is CH2, O or S.
R1 is xe2x80x94Qxe2x80x94CnH2n+1, xe2x80x94Qxe2x80x94(CH2)aCnF2n+1, xe2x80x94Qxe2x80x94CH2OCH2CnF2n+1, xe2x80x94Qxe2x80x94CH2SCH2CCnF2n+1, xe2x80x94Qxe2x80x94CH2OCH2CF3, or xe2x80x94Qxe2x80x94CH2SCH2CF3, where n is 1-10, a is 0-10, and Q is absent, O or S.
More preferably, R1 is C4-C10 or fluorine substituted C4-C10.
A compound having Formula IV can be prepared using a dihydronaphthyl cyclic bridge which preferably comprises Formula VIII: 
Preferably, J is CH2, O or S.
Preferably, R1 is H, xe2x80x94Qxe2x80x94CnH2n+1, xe2x80x94Qxe2x80x94(CH2)aCnF2n+1, xe2x80x94Qxe2x80x94CH2OCH2CnF2n+1, xe2x80x94Qxe2x80x94CH2SCH2CCnF2+1, xe2x80x94Qxe2x80x94CH2OCH2CF3, or xe2x80x94Qxe2x80x94CH2SCH2CF3, where n is 1-10, a is 0-10, and Q is absent, O or S. Other halogens can be used in place of F. In more preferred embodiments of the invention, R1 is C4-C10 or fluorine substituted C4-C10.
X preferably has the formula (Cxe2x95x90O)H or Cxe2x95x90CH(xe2x80x94CHxe2x95x90CH)dxe2x80x94C(xe2x95x90O)H, where d is 0-3. The terminal aldehyde or ketone group serves as the preferred site of reaction with electron withdrawing groups. In more preferred embodiments of the invention, X is (Cxe2x95x90O)H.
Z is a chemical group that is capable of being linked to a donor, as described above.
The present invention is also directed to compounds which can be employed as chromophores in polymeric thin films for optical waveguides wherein the compounds comprise novel bridge groups and novel electron withdrawing groups, and are represented by Formula IV: 
where, K is O or S; and
R1 is xe2x80x94Qxe2x80x94CnH2n+1, xe2x80x94Qxe2x80x94(CH2)aCnF2n+1, xe2x80x94Qxe2x80x94CH2OCH2CnF2+1, xe2x80x94Qxe2x80x94CH2SCH2CCnF2n+1, xe2x80x94Qxe2x80x94CH2OCH2CF3, or xe2x80x94Qxe2x80x94CH2SCH2CF3, where n is 1-10, a is 0-10, and Q is absent, O or S, and q is 1, 2, or 3. In more preferred embodiments of the invention, R1 is C4-C10 or fluorine substituted C4-C10. More preferred compounds of this embodiment of the invention are represented by Formula IVxe2x80x2: 
xe2x80x83where:
R2 and R3 are further characterized in that they define a ring in which * denotes a spiro junction, or where * denotes a chiral center.
Preferably, R2 and R3 each, independently, are selected from the group consisting of, but not limited to, substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted aryl, substituted or unsubstituted alkylaryl, substituted or unsubstituted carbocycle, substituted or unsubstituted heterocycle, substituted or unsubstituted cyclohexyl, (CH2)nxe2x80x94Oxe2x80x94(CH2)n where n is 1-10, and the like. More preferably, R2 and R3 each, independently, are selected from the group consisting of substituted or unsubstituted aryl, substituted or unsubstituted alkylaryl, and substituted or unsubstituted cyclohexyl. More preferably, R2 and R3 each, independently, are selected from the group consisting of benzyl, cyclohexyl, and substituted or unsubstituted phenyl. More preferably, one of R2 and R3 is CH3 and the other of R2 and R3 is a substituted phenyl. Most preferably, one of R2 and R3 is 
and the other of R2 and R3 is CH3.
Alternatively, R2 and R3 together form a ring structure or a substituted ring structure from 3 to 7 atoms total with 5 or 6 atoms being preferred. Preferably, the ring structure is substituted or unsubstituted carbocycle, substituted or unsubstituted heterocycle, or substituted or unsubstituted cyclohexyl or cyclopentyl. The substituted ring structure can comprise substituents including, but hot limited to, deuterium and halides, including fluorine, chlorine and bromine. A preferred compound having a ring structure formed by R2 and R3 comprises 
D is an electron donating group as described above.
In other embodiments of the invention, useful compounds are represented by the structure of Formula V: 
where, J is CH2, O or S.
Preferably, R1 is xe2x80x94Qxe2x80x94CnH2n+1, xe2x80x94Qxe2x80x94(CH2)aCnF2n+1, xe2x80x94Qxe2x80x94CH2OCH2CnF2n+1, xe2x80x94Qxe2x80x94CH2SCH2CCnF2n+1, xe2x80x94Qxe2x80x94CH2OCH2CF3, or xe2x80x94Qxe2x80x94CH2SCH2CF3, where n is 1-10, a is 0-10, and Q is absent, O or S. In more preferred embodiments of the invention, R1 is C4-C10 or fluorine substituted C4-C10. More preferred compounds of this embodiment are represented by the structure of Formula Vxe2x80x2: 
where, R2 and R3 are further characterized in that they define a ring in which * denotes a spiro junction, or where * denotes a chiral center.
Preferably, R2 and R3 each, independently, are selected from the group consisting of, but not limited to, substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C2-C10 alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted alkylaryl, substituted or unsubstituted carbocycle, substituted or unsubstituted heterocycle, substituted or unsubstituted cyclohexyl, (CH2)nxe2x80x94Oxe2x80x94(CH2)n where n is 1-10, and the like. More preferably, R2 and R3 each, independently, are selected from the group consisting of substituted or unsubstituted aryl, substituted or unsubstituted alkylaryl, and substituted or unsubstituted cyclohexyl. More preferably, R2 and R3 each, independently, are selected from the group consisting of benzyl, cyclohexyl, and substituted or unsubstituted phenyl. More preferably, one of R2 and R3 is CH3 and the other of R2 and R3 is a substituted phenyl. Most preferably, one of R2 and R3 is 
and the other of R2 and R3 is CH3.
Alternatively, R2 and R3 together form a ring structure or a substituted ring structure from 3 to 7 atoms total with 5 or 6 atoms being preferred. Preferably, the ring structure is substituted or unsubstituted carbocycle, substituted or unsubstituted heterocycle, or substituted or unsubstituted cyclohexyl. The substituted ring structure can comprise substituents including, but not limited to, deuterium and halides, including fluorine, chlorine and bromine. A preferred compound having a ring structure formed by R2 and R3 comprises 
D is an electron donating group as described above.
The present invention is also directed, in part, to optical waveguides comprising polymeric this films having comprising the chromophores of the invention. In preferred embodiments of the invention, optical waveguides comprising a thin film medium have Formula VI: 
P and Pxe2x80x2 are polymer main chain units, which can be the same mer unit or different mer unit, and C is a comonomer unit where n is an integer greater than zero and nxe2x80x2 is 0 or an integer greater than zero. Polymers and copolymers that may be employed in the present invention are described in, for example, U.S. Pat. Nos. 5,044,725, 4,795,664, 5,247,042, 5,196,509, 4,810,338, 4,936,645, 4,767,169, 5,326,661, 5,187,234, 5,170,461, 5,133,037, 5,106,211, and 5,006,285, each of which is incorporated herein by reference in its entirety. The polymers of the invention can be a homopolymer or a copolymer. Preferred polymers and copolymers include, but are not limited to, acrylate, vinyl carboxylate, substituted arylvinyl, vinyl halide, vinyl carboxylate, alkene, alkadiene, arylvinyl, methacrylate, vinyl chloride, vinyl acetate, vinyl ether, ethylene, propylene, isobutylene, 1-butene, isoprene, styrene, and the like.
Preferably, the polymers of the invention comprise an external field-induced orientation and alignment of pendant side chains. Preferably, the polymer main chain can be a structural type such as polyvinyl, polyoxyalkylene, polysiloxane, polycondensation, and the like. A polymer can be applied to a supporting substrate by conventional means, such as spin coating, dip coating, spraying, Langmuir-Blodgett deposition, and the like. Thin film optical waveguide medium of the present invention after fabrication can be subjected to an external field to orient and align uniaxially the polymer side chains. In one method the polymer medium is heated close to or above the polymer glass transition temperature Tg, then an external field (e.g., a DC electric field) is applied to the medium of mobile chromophore molecules to induce uniaxial molecular alignment of the chromophore polymer side chains or guests in a guest-host system parallel to the applied field, and the medium is cooled while maintaining the external field effect.
S is a pendant spacer group having a linear chain length of between about 2-12 atoms. Pendant spacer groups that may be employed in the present invention are described in, for example, U.S. Pat. Nos. 5,044,725, 4,795,664, 5,247,042, 5,196,509, 4,810,338, 4,936,645, 4,767,169, 5,326,661, 5,187,234, 5,170,461, 5,133,037, 5,106,211, and 5,006,285, each of which is incorporated herein by reference in its entirety.
M is a chromophore compound having Formula I, Formula II, Formula III, Formula IV, or Formula V, described above.
The present invention is also directed, in part, to optical devices comprising the optical waveguides of the invention. Optical devices are described in, for example, U.S. Pat. Nos. 5,044,725, 4,795,664, 5,247,042, 5,196,509, 4,810,338, 4,936,645, 4,767,169, 5,326,661, 5,187,234, 5,170,461, 5,133,037, 5,106,211, and 5,006,285, each of which is incorporated herein by reference in its entirety. Preferred optical devices include, but are not limited to, laser frequency converters, optical interferometric waveguide gates, wideband electrooptical guided wave analog-to-digital converters, optical parametric devices, and the like, as described in U.S. Pat. No. 4,775,215, which is incorporated herein by reference in its entirety.
The invention is further illustrated by way of the following examples which are intended to elucidate the invention. These examples are not intended, nor are they to be construed, as limiting the scope of the disclosure.